The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1887-08-29
THE FORTH BRIDGE.
N Stupendous Structure Eciipsing Anything
of the Kind Yet Erected.

of the Kind Yet Erected.
Edinburgh Letter in louisville Times.
Crossing and recrossng the Firth OF Forth
Few days since, got good sight or the great
Forth bridge that is well on its way TO COM
pleton. 1t will be the wonder and admiration
of the world the browning triumph OF engineer
ing genius and our bold Brooklyn bridge will
have to take a back seat. a distinguished
Yineer recently said of this colossal work, with
out o doubt the Forth bridge is the most stupen-
dous structure attempted to be raised of iron
DR. steel" The whole OF the work of the bridge
s Of steel ''in the cantilever and central girder
system" The entire length of the bridge will
mile and half. The two principal spans
of the structure are LOO feet each in
length, two side spans Of BIS feet each, with the
ends massively supported and three intermediate
piers In the middle of the j. 700 feet span there
Is an unobstructed passage for navigation 100
feet above the high-water mark. From the
foundation OF the loftiest pier TO the top OF the
cantilevers, the height is $50 feet Tor only ten
feet less than the great pyramid OF Egypt"
The most powerful pier weighs 10000 tons.
According to a report made the day previous
10 my view of the structure the materials put
down on the spot up to the present time reckon.
MP 500 900 cubic feet of granite and q. 900 tons
Of Portland cement Thus far l3O,OOo cubic
yards OF masonry had been erected in piers and
Abutments. 49, 900 tons of steel in approaches and
spars. and 10000 more tons of steel is ready for
placing. At this time there are 3, 600 men at Work
In connection with this gigantic undertaking.
and the force will average 5000 men the year
round. Most of the men are quartered about
the busy scene. but special train TO Edln
and a special steamer to Leith daily for the
accommodation of those living in the cities.
Every precaution will be taken to make the
mighty structure absolutely safe. The engin-
GERS will take heed of the terrible catastrophe at
the Tay bridge. and will endeavor 70 make this
proof against the weight of passing trains and
secure from the inroads of the tides and winds.
On this subject. Mr.. Wood, one of the engln-
eers in charge,
"The cross sections of the main spans are of
trapezoida form. $50 feet in height from center
90 ~ . ha har III nd
ty-three and 120 feet in width across top and bot
tom respectively, and tapering towards the ends
of the cantilevers thus giving form which is
eminently suitable for withstanding lateral pres
Jure. The orders carrying the railway are sup
ported at intervals inside the cantilevers by
trestlen cross frames, and q continuous lattice
work parapet four and one-half feet above
the rails extends the whole length of the
bridge. In addition to its own weight the
bridge is being constructed to support without
exceeding any member the unit stresses permit
ted by the Board of Trade load equivalent to
trains of unlimited length equal to ton per
foot run on each line of railway. or passing
trains consisting each OF two engines and tend
ers at the head Of sixty coal trucks weighing
fifteen tons each, and also withstand a lateral
wind pressure Of ifty-six pounds per square
foot of exposed surface of train and structure.
The magnitude Of the lateral pressure may be
judged from the fact that over the mile length
of main spans the estimated surface exposed to
a point-blank wind at right angles to the bridge
amounts to little more than seven and
half across; the pressure OF 6fty-six pounds per
square foot on this surface would therefore be
equivalent to a total or more than s, 600 tons In
addition to lateral winds. the direction from any
point of the compass has been provided for even
including the imaginary condition of each group
Of members becoming the center of a whirl-
wind.
Effects of temperature will be provided for in
the rails and at the junction of the central grid
ers with cantilevers, and the bearings on both
the main piers and under the weighted ends of
the cantilevers have provision made for allowing
movements due to changes of temperature and
to the elasticity OF the cantilevers under lateral
pressure The whole of the piers may act
in concert to resist combined actions of all the
forces tending to disturb the normal state of
rest of the so. 900 tons of permanent load. As
further provision forty-eight steel bolts of
two and one-half inches diameter, secured
twenty four feet down in the masonry by anchor
plates hold down the bed plates with an initial
tension Of two thousand tons. The maximum
pressure on the base of the piers will De little
over six tons per square foot The enormous
forces to be resisted have been met by adopting
the most suitable forms of parts for withstand
ing the stresses Tubular members used for
aad open-traced box forms for ten
sion. The masonry for the main piers above
the open stone concrete filings of the caissons,
consists of a casing Of Aberdeen granite inclosng
and bonded into boarding of Arbrouth stone
set in cement and strengthened by three
sive wrought-iron belts Quilt into the stone
work"
Another engineer, speaking of expansion.
said: The case of Brooklyn bridge was re-
expansion, being provided for within
itself. Expansion had two different directions
and that provided for in the Forth bridge
SO that the cantilevers, left alone, would adjust
themselves The intermediate girder provided
for expansion. and there was no danger to any
point Of the structure"
These statements, figures and facts were
brought about at a meeting of the "Institution
of Mechanical Engineers" which was in session
during my stay in Edin burgh- l attended one
Of the evening entertainments given in honor of
the organization, and saw many of the most dis
tinguished engineers of the English empire.
There were several Japanese ennineers present
Another statement in regard to the wonderful
bridge struck me worth mentioning. zone
feature is the comparative poiselessness with
which the work is being conducted. Hitherto
the construction of iron bridges and viaducts has
been accompanied by the incessant rattle Of the
riveters' hammers, but here immense struct
urs of steel is being raised with amazing
,elerity and the sound of riveting is practically
unknown"
PHIL ARMOUR'S GOOD SENSE.